Abstract:
“Prolonged periods of sleep restriction seem to be common in the contemporary world. Sleep loss causes perturbations of circadian rhythmicity and degradation of waking alertness as reflected in attention, cognitive efficiency and memory. Understanding whether and how the human brain recovers from chronic sleep loss is important not only from a scientific but also from a public health perspective. In this work we report on behavioral, motor, and neurophysiological correlates of sleep loss in healthy adults in an unprecedented study conducted in natural conditions and comprising 21 consecutive days divided into periods of 4 days of regular life (a baseline), 10 days of chronic partial sleep restriction (30% reduction relative to individual sleep need) and 7 days of recovery. Throughout the whole experiment we continuously measured the spontaneous locomotor activity by means of actigraphy with 1-minute resolution. On a daily basis the subjects were undergoing EEG measurements (64-electrodes with 500 Hz sampling frequency): resting state with eyes open and closed (8 minutes long each) followed by Stroop task lasting 22 minutes. Altogether we analyzed actigraphy (distributions of rest and activity durations), behavioral measures (reaction times and accuracy from Stroop task) and EEG (amplitudes, latencies and scalp maps of event-related potentials from Stroop task and power spectra from resting states). We observed unanimous deterioration in all the measures during sleep restriction. Further results indicate that a week of recovery subsequent to prolonged periods of sleep restriction is insufficient to recover fully. Only one measure (mean reaction time in Stroop task) reverted to baseline values, while the others did not.”
Sleep deficiency is well known to negatively impact human functioning. For example, it is associated with deficits in attention and memory, as well as increased risk of car accidents, heart problems, and other medical issues. However, while some research has addressed recovery after chronic sleep deprivation, it has been unclear how much time is needed to fully recover from prolonged periods of deficient sleep.
To shed more light on this topic, Ochab and colleagues conducted a small study with several healthy adults who underwent 10 days of purposeful sleep restriction followed by 7 recovery days of unrestricted sleep. Participants completed the study in their normal day-to-day environments and wore wrist sensors to monitor daily patterns of sleep and activity. They also underwent daily electroencephalography (EEG) to monitor brain activity, and they answered daily questions (Stroop tasks) to measure reaction times and accuracy.
After 7 days of recovery, the participants had not yet returned to pre-sleep deprivation performance on most measures of functioning. These included several EEG measures of brain activity, rest-versus-activity patterns captured by wrist sensors, and accuracy on Stroop tasks. Only their reaction times had recovered to baseline levels.
While the researchers note that it is difficult to compare these results with other studies that employed different methods, the findings contribute new insights into recovery from chronic sleep loss. Future research could expand to a greater number of participants, investigate longer recovery periods, and disentangle the order in which different functions return to normal.
The authors add: “The investigation of the recovery process following an extended period of sleep restriction reveal that the differences in behavioral, motor, and neurophysiological responses to both sleep loss and recovery.”
